Hello, my name is Caleb. I am a rising senior attending New Vista High School.  I have always been fascinated in technology and how it functions. My first start to discovering my interest in engineering, began with my high school robotics club. It provided a social and fun environment involving the creation of awesome robots. I realized that engineering might be the career I want to pursue.  My starter projects are “MintyBoost V3.0” and the voice changer. My intensive project is the light harp.

Bill of materials          High School           Instructables          Starter Project

Milestone 3 Goal: Finished Result

My third milestone video was taken the second to last day of Blue Stamp. It is completely finished, with the gold paint job and everything. It has full functionality, and no errors I have not fixed. The multiplexer is working good, the frame is functioning and not flimsy, the lasers align with the photodiodes, the programming is flawless with easy edibility, and it’s gold.


  • Button
  • Gold metallic paint
  • Two multiplexers




Since the last milestone video, the coding has been added and fixed. The multiplexer works by connecting it to digital outputs, and telling it to switch channels. I used a “for loop”, which is a function in arduino that allows you to change a variable’s value quickly. I made the “for loop” to link to the digital outputs, so they would be constantly changing on and off in different combinations (1-13 for each multiplexer). I also added a “bitread” which is a function that only uses 0 and 1 (yes or no). I used the “bitread” function and a lot of “if” statements to determine if the pin would be on or off. Each multiplexer required 4 digital pins. This meant I had a total of 16 combinations (because of binary). For example, if all four pins read NO, NO, NO, NO, then it would read channel 0 on the multiplexer. If the pins read NO, NO, NO, YES, then it would be 1, etc. I only used 13 of the combinations on each multiplexer because I only had 13 lasers and photodiodes. To summarize how the multiplexer works, it turns 1 analog input into 16 analog inputs.

After I learned all of the functions that were in the original arduino sketch, it was easy to redesign it to what I needed. I just lengthened the amount of notes, added the multiplexing, created more variables to correspond with the added lasers, and changed some variables.



Milestone 2 Goal: Finish the Frame and the Soldering

My second milestone was postponed for a lengthened period of time because my first prototype did not suit what I wanted. My second milestone required more assignments than I previously thought, such as…

  • 3D print photodiode and laser housing I created with sketchup
  • Solder 26 photodiodes with 6 solder connections each
  • Solder 26 lasers with 3 solder connections each
  • Build a faulty prototype
  • Visit a thrift store for a new frame
  • Replicate said frame with better material
  • Measure dimensions on flat sheets of wood
  • Cut large rectangles out of wooden planks
  • Screw and glue the wooden planks together accordingly
  • Align lasers with plyers and hot glue



  • Half inch thick plywood for the frame
  • Quarter inch thick sanded plywood for the frame
  • Black, Red, Blue, and Yellow unthreaded copper wire for making connections
  • 26 total lasers
  • 26 total photodiodes
  • Hot glue (A lot of it) to align lasers
  • Variety of screws to fix the frame together
  • Hinges and a latch to make it expandable and able to close
  • Ableton Live 9 to recognize the arduino as a MIDI controller
  • 5v portable rechargeable battery to power the lasers

Photodiode House   Photodiode Housing

laser housing   Laser Housing



The lasers and photodiodes have the same mechanism as in the previous milestone description (see circuit diagram). The only difference is instead of 2, there are now 26. The harp is not able to create sound due to lack of coding. This milestone is strictly for the hardware and frame. The photodiodes fit in their housings perfectly, but the lasers had trouble with theirs. I had to drill the hole a bit wider so I could wiggle them around for alignment. The lasers eventually lined up with the photodiodes perfectly, and was just waiting the coding to be finished. The frame is strong and fastened with screws. It open and closes thoroughly. The wiring all fits within the space I have given it, so there are shorting problems or broken solder connections.


Milestone 1 Goal: Making more than 1 laser function and produce sound

My first milestone occurred sooner than I had originally anticipated. The Instructables page I was imitating had clear instructions and there were only a few. I used a breadboard for the circuit before soldering everything together. All of the arduino code was in a file that I downloaded from the page, and assembling the circuit was incredibly simple. I finished it within a couple hours or so. I only had trouble fixing the lasers with the photodiodes. After I finished testing them, I looked for a software to run a MIDI controller. A MIDI controller is a device that is recognized by many music softwares. An input MIDI controller, such as a piano or button pad, allows the user to input signals to softwares that accept MIDI. It took me near 4 hours to find a software that worked correctly. I’m glad I extended my search because the software I found, Ableton Live 9, has hundreds of instruments and sound effects I can choose from.


  • 100k resistors (R1-R6) are used for photodiodes. The resistance is so high due to the low resistance that the photodiode uses.
  • 100 resistors (R7-R12) are used for the lasers to prevent the lasers from receiving  too much voltage.
  • Photodiodes (P1-P6) are used to send a signal to the arduino by putting a light beam from a laser in contact with it. When contact with the beam is broken, the signal drops. When my code notices the signal dropping, it plays a note.
  • Lasers (LED1-LED6) send a beam of light to the photodiodes.

FEXANR7HR0AQM15.MEDIUM   Circuit Diagram


I assembled two lasers on a breadboard with a 100 ohm resistor as shown in the circuit diagram below. The laser require 5 volts to work, so I used the 5v output on the arduino to power them. I extended the circuit with another breadboard so I could distance the photodiodes and lasers better. I used a sum of wires to carry all the connections to where they needed to be. The wire in between the photodiode and the 100k ohm resistor leads to the analog input. When the photodiode receives the red beam from the laser, it undergoes a complicated process of creating electron pairs. In summary, it increases the current that flows to the analog input. When the beam is blocked, the current going to the analog input is dramatically decreased. I configured my arduino sketch to recognize the change in current so it will play a note. I did not learn too much arduino, because I downloaded the sketch file from the Instructables I was following (link below).



MintyBoost Phone Charger Starter Project

For my starter project, I chose to construct the “MintyBoost v3.0”, which operates as a portable phone charger powered by two AA batteries. The components are generally simple, and work as an energy converter. The batteries themselves export roughly 3V together, so an energy converter was necessary for the design. A more specific title for gadgets like this is known as a DC-DC converter.


Purpose of each component & location on circuit schematic:

  • Resistors (R4, R3, R2, R1) are used as a voltage divider to help apple devices identify the MintyBoost as a charger by transmitting a certain voltage through the USB. This is because Apple is silly, and wants you spend money on only their products.
  • The power inductor (L1) is used to regulate the current passing through it and temporarily hold energy to help increase voltage output.
  • The schottky diode (D1) is a semiconductor that slightly lowers voltage passing through it. It also only allows the energy current to flow outward.
  • The 5 volt boost converter (IC1) is the heart of the device that has an internal switch. The switch will flick off and on to help build up energy in the inductor.
  • The power supply capacitors (C3, C4) are quick reacting agents that maintain the power supply if there is a sudden change in energy input.
  • The bypass capacitors (C1, C2) are placed to turn an alternating current into a direct current. It smoothens the energy current that passes through it.
  • The female USB jack (X1) is where you plug in your USB cord to connect to your device.
  • The final resistor (R5) is used in the boost converter, though it’s usage is complicated.



Voice Changer Starter Project

My first starter project “MintyBoost” was not compatible with my iPhone 4 because of Apple’s stubborn marketing strategies. I was given the choice of making a second starter project, so I chose the voice changer. The voice changer does exactly what you would expect it to. It can change your voice in 4 different settings; robot, vibrato, high pitch, and low pitch. The voice changer includes a volume control, an On/Off switch, and a mic sensitivity control.


Purpose of each component & location on schematic:

  • The power switch (SW1) grants magical wishes (Turns the power on and off).
  • The zener diode only allows current to flow in one direction UNLESS a certain voltage is met which will allow it to flow the other way.
  • The capacitors (C1-C4) are used to smooth electric current as well as the electrolytic capacitors (C5-C10), which have the same properties except the electrolytic capacitors can withstand much more energy.
  • The resistors (R1-R10) lower current flow.
  • The pushbuttons complete a circuit that leads to the HT8950 chip in order to change a variable.
  • The LED lights (LD1, LD2) light up to inform the user if the power is on, and if the microphone is receiving input.
  • The horizontal trimmer (RV1) acts as an adjustable resistor that can increase or decrease depending on its setting. It controls the current output of the microphone.
  • The capacitors (C1, C2, C3, C4) hold energy and can smoothen a current.
  • The microphone (mic1)  intakes sound waves and converts them into electrical energy.
  • The electrolytic capacitors (C5-C10) can store energy and smoothen a current.
  • the vertical trimmer (RV2), aka volume control, is similar to the horizontal trimmer. It acts like an adjustable resistor for current flow.
  • The HT8950 (IC1) is an integrated circuit that changes the alternating current depending on its setting.
  • The LM386N (IC2) is an amplifier that increases the current going towards the speaker.



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